1. Field of the Invention
The subject invention generally relates to a ladder having excellent strength, rigidity, and weight.
2. Description of the Related Art
Generally, ladders, including fixed ladders, step ladders, step stools, and extension ladders, are formed from metals or combinations of metals and fiberglass. Metals and/or fiberglass are generally known to have excellent strength. However, even ladders formed from these materials may lack structural features which impart the ladder with sufficient strength and rigidity for use. Ladders formed from metals or combinations of metals and fiberglass can also be heavy and therefore difficult to manipulate and use. Additionally, ladders formed from metals generally require a significant amount of linkages, such as rivets or spot welding, therefore substantially increasing production time and cost of these ladders. Use of metals in ladders is further prohibitive in view of the increased cost of metals, such as aluminum and steel. One alternative material to metal which may be used to form ladders is thermoplastics.
While thermoplastics are often cheaper than metals, thermoplastics are not generally known for possessing those physical properties typical of metals, e.g. excellent strength and rigidity, which are required to form a safe, sturdy, and useful ladder. Accordingly, ladders formed from thermoplastics generally require more material than ladders formed from metals to impart the thermoplastic ladders with sufficient strength and rigidity, resulting in thermoplastic ladders that are generally heavier and therefore more difficult to operate than ladders formed from metals. One method to improve the strength of thermoplastics, and to reduce overall weight of ladders formed therefrom, is to include reinforcing fibers, such as glass fibers (fiberglass). Although thermoplastics reinforced with fiberglass have increased strength, ladders formed from these materials are still typically heavy and are therefore difficult to manipulate and operate.
Despite efforts using different materials such as metals, thermoplastics, or thermoplastics including reinforcing fibers to form ladders, concerns remain regarding the strength, rigidity, and weight of these ladders. Accordingly, there remains an opportunity to form an improved ladder.